I recently:
upgrade my Android Studio to 3.0 stable channel
checkout my project hosted on SVN and which was on git 6 months ago.
My IDE is reading the project as it is on git and not on SVN => I want to disconnect it from git and commit changes only on SVN .
REM : I didn't face this behaviour when it was on Android Studio 2.3 stable channel
You should be able to change the version control settings in the ./.idea/vcs.xml
file:
<project version="4">
<component name="VcsDirectoryMappings">
<mapping directory="$PROJECT_DIR$" vcs="Git" />
</component>
</project>
Change Git to SVN and reload the project in the IDE. I'm not sure if you can change that setting within the IDE settings itself, but this should be a simple change.
You can also try and simply delete the ".git" sub directory.